Background of the Invention
The present invention relates to an innovative mechanical transmission for toy electric cars for children. In the known art toy electric cars for children are usually equipped with 2-speed transmissions realized by an electric switch which connects the motor to the entire battery package or to a single part thereof so that it is powered at full voltage, which corresponds to the high gear, or reduced voltage, e.g. half, corresponding to low gear. This solution has however the disadvantage that at the lower gear there is a corresponding lesser power delivered to the motor, which is exactly opposite to what is normally desired from a transmission. In addition, during design it is not possible to determine freely the speed ratio between the two speeds since it is dependence on the electrical parameters of the motor, even allowing for the fact than below a certain input voltage the motor would tend to stop at the slightest additional effort. On the other hand known mechanical transmissions are considered excessively complicated and costly for use in a toy automobile because they assume the existence of a disengageable clutch with pedal for changeover between the various speeds, which would complicate control of the toy car by the child.
A draw-key type transmission which includes a plurality of gears rotatably mounted on a transmission shaft with key means movable longitudinally along the shaft to engage between the shaft and a selected gear of the plurality is also known from the prior art. The known transmissions are however, achieved so that they transmit relatively high torques and turn out to be encumbering and expensive for being applied on toy vehicles. For example, U.S. Pat. No. 3,890,850 discloses a transmission for vehicles such as riding lawn mowers. The transmission is made up with many and complex parts and comprises a rotatably-mounted-shaft. An output gear is keyed on an end of the shaft. On the shaft two sleeves are inserted. Gears are freely rotatably mounted on the sleeves and mesh with corresponding input gears. Engageable means sliding in the sleeves by a shifter fork which is pivoted by a shift lever. In this manner, the engageable means engages between the shaft and a selected gears on the sleeves. U.S. Pat. No. 5,099,713 discloses a transmission for tractors, which comprises a hollow shaft supported b bearings. Gears are freely rotatably mounted on the shaft and mesh with corresponding input gears. The shaft accommodates an axially slidable rod which, when moved, forces the pins radially to couple the shaft to the corresponding input gear. The achieved transmission is however highly encumbering, complex and expensive to be applied on toys.